Fusaria of Potatoes 



221 



substratum, on potato agar rich in glucose, vinaceous lilac, varying from 

 colorless and orange vinaceous to pome- 

 granate purple and vinaceous purple; 

 plectenchymic sporodochia common on 

 most of the media; bluish black sclerotia 

 (up to 3 millimeters in diameter) con- 

 stantly present on potato tuber plug and 

 sometimes on different agars. 



Hab. In fibrovascular bundles of 

 diseased stems and tubers of Solarium 

 tuberosum, in the United States, perhaps 

 also in Europe, Africa, and other regions, 

 also on Lycopersicum esculentum Vigna, 

 and Pisum. 



The organism was isolated alone and in 

 association with several other Fusaria, 

 several times from various localities in 

 New York and in other States. The de- 

 scription given above is based on the study 

 of the culture obtained through the cour- 

 tesy of Dr. Wollenweber. 



Measurements of the conidia are as 

 follows: 



On slightly acidified hard potato agar, 

 culture nineteen days old; conidia from 

 aerial mycelium close to substratum: 



Conidia: 0-septate, 87 per cent, 8x2.9 (4.5-12x2-4)/* 



1-septate, 6 per cent, 16.5x3.4 (11-23x2.5-4.1)/* 

 2-septate, 1 per cent, 18.5x3.9 (17-26 x 3-4.2)/* 

 3-septate, 5 per cent, 27.5 x 4 (15-39 x 3-4.7) /* 

 4-septate, 1 per cent, about 40x4.5 (36-44 x 4.3-4.8) /* 



On hard lima-bean agar, culture twelve days old; conidia from aerial 

 mycelium : 



Conidia: 0-septate, 99 per cent, 6.5 x 2.6 (4.5-16 x 1.75-3.5)/* 

 1-septate, 1 per cent, 14 x 3.2 (10-17 x 3-3.5)/* 



Fig. 35. — a, Fusarium oxysporum, 



sporodochial conidia 

 b-.i, F. oxysporum var. asclerotium: 



b, Conidia from 14-days-old culture 

 on slightly acidified hard potato agar; 



c, conidia from 46 -days -old culture 

 on red raspberry cane plug; d, conidia 

 from 7-days-old culture on hard 

 lima-bean agar; e, chlamydospores 

 from 46-days-old culture on red 

 raspberry cane plug; f, terminal 

 chlamydospores produced on normal 

 conidiophores, g and h, conidio- 

 phores (h magnified 250 times) from 

 1^-days-old culture on slightly acidi- 

 fied hard potato agar; i, chlamydo- 

 spores from 25-days-old culture on 

 corn agar; j, conidiophores from 

 7-days-old culture on hard lima-bean 

 agar 



